feat: ability to redeposit or extract unclaimable bribes

src/BribeInitiative.sol

@@ -4,7 +4,7 @@ pragma solidity 0.8.24;
 import {IERC20} from "openzeppelin/contracts/interfaces/IERC20.sol";
 import {SafeERC20} from "openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 
-import {IGovernance} from "./interfaces/IGovernance.sol";
+import {IGovernance, UNREGISTERED_INITIATIVE} from "./interfaces/IGovernance.sol";
 import {IInitiative} from "./interfaces/IInitiative.sol";
 import {IBribeInitiative} from "./interfaces/IBribeInitiative.sol";
 
@@ -78,6 +78,73 @@ contract BribeInitiative is IInitiative, IBribeInitiative {
         bribeToken.safeTransferFrom(msg.sender, address(this), _bribeTokenAmount);
     }
 
+    function _getValidatedLQTYAllocation(
+        DoubleLinkedList.List storage _list,
+        uint256 _epoch,
+        uint256 _prevAllocationEpoch,
+        string memory _errorMsg
+    ) internal view returns (DoubleLinkedList.Item memory _item) {
+        if (_prevAllocationEpoch == 0) {
+            require(_list.isEmpty(), _errorMsg);
+            // Leaving _item uninitialized, as there's never been an allocation
+        } else {
+            require(_list.contains(_prevAllocationEpoch), _errorMsg);
+            _item = _list.getItem(_prevAllocationEpoch);
+            require(_prevAllocationEpoch <= _epoch && (_item.next > _epoch || _item.next == 0), _errorMsg);
+        }
+    }
+
+    // Returns true if there are no existing LQTY allocations to the initiative, and there's no possibility of
+    // allocating any more because the initiative's been unregistered.
+    function _noPresentOrFutureAllocation() internal view returns (bool) {
+        // Note that the initiative could already be unregisterable but not yet unregistered, which we ignore here.
+        // In that case, the stuck bribes can always be extracted in the next epoch _after_ unregistering the initiative.
+        uint256 latestTotalAllocationEpoch = getMostRecentTotalEpoch();
+        return (
+            latestTotalAllocationEpoch == 0 || totalLQTYAllocationByEpoch.getItem(latestTotalAllocationEpoch).lqty == 0
+        ) && governance.registeredInitiatives(address(this)) == UNREGISTERED_INITIATIVE;
+    }
+
+    /// @inheritdoc IBribeInitiative
+    function redepositBribe(uint256 _originalEpoch, uint256 _prevTotalLQTYAllocationEpoch) external {
+        Bribe memory bribe = bribeByEpoch[_originalEpoch];
+        require(bribe.remainingBoldAmount != 0 || bribe.remainingBribeTokenAmount != 0, "BribeInitiative: no-bribe");
+
+        DoubleLinkedList.Item memory totalLQTYAllocation = _getValidatedLQTYAllocation(
+            totalLQTYAllocationByEpoch,
+            _originalEpoch,
+            _prevTotalLQTYAllocationEpoch,
+            "BribeInitiative: invalid-prev-total-lqty-allocation-epoch"
+        );
+
+        require(totalLQTYAllocation.lqty == 0, "BribeInitiative: total-lqty-allocation-not-zero");
+        assert(bribe.claimedVotes == 0); // Can't possibly have claimed anything
+
+        if (_noPresentOrFutureAllocation()) {
+            if (bribe.remainingBoldAmount != 0) {
+                bold.safeTransfer(msg.sender, bribe.remainingBoldAmount);
+            }
+            if (bribe.remainingBribeTokenAmount != 0) {
+                bribeToken.safeTransfer(msg.sender, bribe.remainingBribeTokenAmount);
+            }
+
+            emit ExtractUnclaimableBribe(
+                msg.sender, _originalEpoch, bribe.remainingBoldAmount, bribe.remainingBribeTokenAmount
+            );
+        } else {
+            uint256 currentEpoch = governance.epoch();
+            bribeByEpoch[currentEpoch].remainingBoldAmount += bribe.remainingBoldAmount;
+            bribeByEpoch[currentEpoch].remainingBribeTokenAmount += bribe.remainingBribeTokenAmount;
+
+            emit RedepositBribe(
+                msg.sender, bribe.remainingBoldAmount, bribe.remainingBribeTokenAmount, _originalEpoch, currentEpoch
+            );
+        }
+
+        delete bribeByEpoch[_originalEpoch].remainingBoldAmount;
+        delete bribeByEpoch[_originalEpoch].remainingBribeTokenAmount;
+    }
+
     function _claimBribe(
         address _user,
         uint256 _epoch,
@@ -90,18 +157,16 @@ contract BribeInitiative is IInitiative, IBribeInitiative {
         Bribe memory bribe = bribeByEpoch[_epoch];
         require(bribe.remainingBoldAmount != 0 || bribe.remainingBribeTokenAmount != 0, "BribeInitiative: no-bribe");
 
-        DoubleLinkedList.Item memory lqtyAllocation =
-            lqtyAllocationByUserAtEpoch[_user].getItem(_prevLQTYAllocationEpoch);
-
-        require(
-            _prevLQTYAllocationEpoch <= _epoch && (lqtyAllocation.next > _epoch || lqtyAllocation.next == 0),
+        DoubleLinkedList.Item memory lqtyAllocation = _getValidatedLQTYAllocation(
+            lqtyAllocationByUserAtEpoch[_user],
+            _epoch,
+            _prevLQTYAllocationEpoch,
             "BribeInitiative: invalid-prev-lqty-allocation-epoch"
         );
-        DoubleLinkedList.Item memory totalLQTYAllocation =
-            totalLQTYAllocationByEpoch.getItem(_prevTotalLQTYAllocationEpoch);
-        require(
-            _prevTotalLQTYAllocationEpoch <= _epoch
-                && (totalLQTYAllocation.next > _epoch || totalLQTYAllocation.next == 0),
+        DoubleLinkedList.Item memory totalLQTYAllocation = _getValidatedLQTYAllocation(
+            totalLQTYAllocationByEpoch,
+            _epoch,
+            _prevTotalLQTYAllocationEpoch,
             "BribeInitiative: invalid-prev-total-lqty-allocation-epoch"
         );
 
@@ -188,7 +253,7 @@ contract BribeInitiative is IInitiative, IBribeInitiative {
     }
 
     /// @inheritdoc IBribeInitiative
-    function getMostRecentTotalEpoch() external view returns (uint256) {
+    function getMostRecentTotalEpoch() public view returns (uint256) {
         uint256 mostRecentTotalEpoch = totalLQTYAllocationByEpoch.getHead();
 
         return mostRecentTotalEpoch;

src/Governance.sol

@@ -5,7 +5,7 @@ import {IERC20} from "openzeppelin/contracts/interfaces/IERC20.sol";
 import {SafeERC20} from "openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 import {ReentrancyGuard} from "openzeppelin/contracts/utils/ReentrancyGuard.sol";
 
-import {IGovernance} from "./interfaces/IGovernance.sol";
+import {IGovernance, UNREGISTERED_INITIATIVE} from "./interfaces/IGovernance.sol";
 import {IInitiative} from "./interfaces/IInitiative.sol";
 import {ILQTYStaking} from "./interfaces/ILQTYStaking.sol";
 
@@ -74,8 +74,6 @@ contract Governance is MultiDelegateCall, UserProxyFactory, ReentrancyGuard, Own
     /// @inheritdoc IGovernance
     mapping(address => uint256) public override registeredInitiatives;
 
-    uint256 constant UNREGISTERED_INITIATIVE = type(uint256).max;
-
     constructor(
         address _lqty,
         address _lusd,

src/interfaces/IBribeInitiative.sol

@@ -7,9 +7,13 @@ import {IGovernance} from "./IGovernance.sol";
 
 interface IBribeInitiative {
     event DepositBribe(address depositor, uint256 boldAmount, uint256 bribeTokenAmount, uint256 epoch);
+    event RedepositBribe(
+        address depositor, uint256 boldAmount, uint256 bribeTokenAmount, uint256 originalEpoch, uint256 newEpoch
+    );
     event ModifyLQTYAllocation(address user, uint256 epoch, uint256 lqtyAllocated, uint256 offset);
     event ModifyTotalLQTYAllocation(uint256 epoch, uint256 totalLQTYAllocated, uint256 offset);
     event ClaimBribe(address user, uint256 epoch, uint256 boldAmount, uint256 bribeTokenAmount);
+    event ExtractUnclaimableBribe(address recipient, uint256 epoch, uint256 boldAmount, uint256 bribeTokenAmount);
 
     /// @notice Address of the governance contract
     /// @return governance Adress of the governance contract
@@ -70,6 +74,14 @@ interface IBribeInitiative {
     /// @param _epoch Epoch at which the bribe is deposited
     function depositBribe(uint256 _boldAmount, uint256 _bribeTokenAmount, uint256 _epoch) external;
 
+    /// @notice Take previously deposited BOLD and/or bribe tokens from an epoch in which nobody voted for the
+    ///         initiative and deposit them as bribes into the current epoch. In case there are no present LQTY
+    ///         allocations, and it's no longer possible to allocate LQTY to the initiative because it's been
+    ///         unregistered, the bribes are paid out to the caller instead.
+    /// @param _originalEpoch Epoch at which the bribes were originally deposited
+    /// @param _prevTotalLQTYAllocationEpoch Epoch at which the total allocated LQTY became zero
+    function redepositBribe(uint256 _originalEpoch, uint256 _prevTotalLQTYAllocationEpoch) external;
+
     struct ClaimData {
         // Epoch at which the user wants to claim the bribes
         uint256 epoch;

src/interfaces/IGovernance.sol

@@ -7,6 +7,8 @@ import {ILQTYStaking} from "./ILQTYStaking.sol";
 
 import {PermitParams} from "../utils/Types.sol";
 
+uint256 constant UNREGISTERED_INITIATIVE = type(uint256).max;
+
 interface IGovernance {
     /// @notice Emitted when a user deposits LQTY
     /// @param user The account depositing LQTY
@@ -216,7 +218,9 @@ interface IGovernance {
 
     /// @notice Returns when an initiative was registered
     /// @param _initiative Address of the initiative
-    /// @return atEpoch Epoch at which the initiative was registered
+    /// @return atEpoch If `_initiative` is an active initiative, returns the epoch at which it was registered.
+    ///                 If `_initiative` hasn't been registered, returns 0.
+    ///                 If `_initiative` has been unregistered, returns `UNREGISTERED_INITIATIVE`.
     function registeredInitiatives(address _initiative) external view returns (uint256 atEpoch);
 
     /*//////////////////////////////////////////////////////////////

src/utils/DoubleLinkedList.sol

@@ -76,6 +76,10 @@ library DoubleLinkedList {
         return (list.items[id].prev != 0 || list.items[id].next != 0 || list.items[0].next == id);
     }
 
+    function isEmpty(List storage list) internal view returns (bool) {
+        return list.items[0].next == 0;
+    }
+
     /// @notice Inserts an item with `id` in the list before item `next`
     /// - if `next` is 0, the item is inserted at the start (head) of the list
     /// @dev This function should not be called with an `id` that is already in the list.

test/BribeInitiative.t.sol

@@ -802,8 +802,8 @@ contract BribeInitiativeTest is Test, MockStakingV1Deployer {
         vm.startPrank(user1);
         BribeInitiative.ClaimData[] memory epochs = new BribeInitiative.ClaimData[](1);
         epochs[0].epoch = governance.epoch() - 1;
-        epochs[0].prevLQTYAllocationEpoch = governance.epoch() - 2;
-        epochs[0].prevTotalLQTYAllocationEpoch = governance.epoch() - 2;
+        epochs[0].prevLQTYAllocationEpoch = 0;
+        epochs[0].prevTotalLQTYAllocationEpoch = 0;
         vm.expectRevert("BribeInitiative: total-lqty-allocation-zero");
         (uint256 boldAmount, uint256 bribeTokenAmount) = bribeInitiative.claimBribes(epochs);
         vm.stopPrank();
@@ -922,6 +922,113 @@ contract BribeInitiativeTest is Test, MockStakingV1Deployer {
         assertEqDecimal(lqtyBribe, bribeAmount / 2, 18, "user1 didn't get their fair share of LQTY");
     }
 
+    function test_RedepositBribe_Reverts_WhenNoUnclaimableBribes() external {
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        uint256 currentEpoch = governance.epoch();
+        vm.expectRevert("BribeInitiative: no-bribe");
+        bribeInitiative.redepositBribe(currentEpoch - 1, 0);
+    }
+
+    function test_RedepositBribe_Reverts_WhenPrevTotalLQTYAllocationEpochIsWrong() external {
+        // No allocations initially
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Some bribes and some allocations an epoch later
+        _depositBribe(1 ether, 1 ether, governance.epoch());
+        _stakeLQTY(user1, 1 ether);
+        _allocateLQTY(user1, 1 ether, 0);
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Attempt to redeposit the previous epoch's bribes while pointing
+        // to the initial epoch as latest total allocation epoch
+        uint256 currentEpoch = governance.epoch();
+        vm.expectRevert("BribeInitiative: invalid-prev-total-lqty-allocation-epoch");
+        bribeInitiative.redepositBribe(currentEpoch - 1, currentEpoch - 2);
+    }
+
+    function test_RedepositBribe_Reverts_WhenBribesAreClaimable() external {
+        // Wait for warm-up to finish
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Some bribes and some allocations
+        _depositBribe(1 ether, 1 ether, governance.epoch());
+        _stakeLQTY(user1, 1 ether);
+        _allocateLQTY(user1, 1 ether, 0);
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Attempt to redeposit the previous epoch's bribes
+        uint256 currentEpoch = governance.epoch();
+        vm.expectRevert("BribeInitiative: total-lqty-allocation-not-zero");
+        bribeInitiative.redepositBribe(currentEpoch - 1, currentEpoch - 1);
+    }
+
+    function test_UnclaimableBribes_WhenInitiativeIsNotUnregistered_CanBeRedeposited() external {
+        uint256 unclaimableBoldAmount = 1e5 ether;
+        uint256 unclaimableBribeTokenAmount = 2e5 ether;
+        _depositBribe(unclaimableBoldAmount, unclaimableBribeTokenAmount, governance.epoch());
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Redeposit bribes and allocate on the initiative
+        bribeInitiative.redepositBribe(governance.epoch() - 1, 0);
+        _stakeLQTY(user1, 1 ether);
+        _allocateLQTY(user1, 1 ether, 0);
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        // Claim redeposited bribes an epoch later
+        uint256 currentEpoch = governance.epoch();
+        (uint256 claimedBoldAmount, uint256 claimedBribeTokenAmount) =
+            _claimBribe(user1, currentEpoch - 1, currentEpoch - 1, currentEpoch - 1);
+
+        assertEqDecimal(claimedBoldAmount, unclaimableBoldAmount, 18, "claimedBoldAmount != unclaimableBoldAmount");
+        assertEqDecimal(
+            claimedBribeTokenAmount,
+            unclaimableBribeTokenAmount,
+            18,
+            "claimedBribeTokenAmount != unclaimableBribeTokenAmount"
+        );
+    }
+
+    function test_UnclaimableBribes_WhenInitiativeIsNotUnregistered_CannotBeRedepositedTwiceFromTheSameEpoch()
+        external
+    {
+        _depositBribe(1e5 ether, 2e5 ether, governance.epoch());
+
+        vm.warp(block.timestamp + EPOCH_DURATION);
+
+        uint256 currentEpoch = governance.epoch();
+        bribeInitiative.redepositBribe(currentEpoch - 1, 0);
+        vm.expectRevert("BribeInitiative: no-bribe");
+        bribeInitiative.redepositBribe(currentEpoch - 1, 0);
+    }
+
+    function test_UnclaimableBribes_WhenInitiativeIsUnregistered_CanBeExtracted() external {
+        uint256 unclaimableBoldAmount = 1e5 ether;
+        uint256 unclaimableBribeTokenAmount = 2e5 ether;
+        _depositBribe(unclaimableBoldAmount, unclaimableBribeTokenAmount, governance.epoch());
+
+        vm.warp(block.timestamp + 5 * EPOCH_DURATION);
+
+        // Unregister initiative then extract stuck bribes
+        governance.unregisterInitiative(address(bribeInitiative));
+        bribeInitiative.redepositBribe(governance.epoch() - 5, 0);
+
+        assertEqDecimal(
+            lusd.balanceOf(address(this)), unclaimableBoldAmount, 18, "claimedBoldAmount != unclaimableBoldAmount"
+        );
+        assertEqDecimal(
+            lqty.balanceOf(address(this)),
+            unclaimableBribeTokenAmount,
+            18,
+            "claimedBribeTokenAmount != unclaimableBribeTokenAmount"
+        );
+    }
+
     /**
      * Helpers
      */